Angiogenesis is a physiological process in which new blood vessels grow from pre-existing ones. This growth may be spontaneous formation of blood vessels or alternatively by the splitting of new blood vessels from existing ones.
Angiogenesis is a normal process in growth and development and in wound healing. It may play a key role in various healing processes among mammals. Among the various growth factors that influence angiogenesis naturally occurring vascular endothelial growth factor (VEGF) is known to be a major contributor by increasing the number of capillaries in a given network. VEGF is a signal protein produced by cells that stimulates angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate. VEGF's normal function is to create new blood vessels during embryonic development, new blood vessels after injury, muscles following exercise, and new vessels to bypass blocked vessels
The process of angiogenesis may be a target for fighting diseases that are characterized by either under development of blood vessels or overdevelopment. The presence of blood vessels, where there should be none may affect the properties of a tissue and may cause for example, disease or failure. Alternatively, the absence of blood vessels may inhibit repair or essential functions of a particular tissue. Several diseases such as ischemic chronic wounds are the result of failure or insufficient blood vessel formation and may be treated by a local expansion of blood vessels. Other diseases, such as age-related macular degeneration may be stimulated by expansion of blood vessels in the eye, interfering with normal eye functions.
In 1971, J. Folkman published in the New England Journal of Medicine, a hypothesis that tumor growth is angiogenesis dependent. Folkman introduced the concept that tumor is probably secrete diffusable molecules that could stimulate the growth of new blood vessels toward the tumor and that the resulting tumor blood vessel growth could conceivably be prevented or interrupted by angiogenesis inhibitors
Tumor angiogenesis is the proliferation of a network of blood vessels that penetrates into cancerous growths supplying nutrients and oxygen while removing waste. The process actually starts with cancerous tumor cells releasing molecules that signal surrounding host tissue, thus activating the release of certain proteins, which encourage growth of new blood vessels. Angiogenesis inhibitors are drugs that block the development of new blood vessels, and. By blocking the development of new blood vessels. Researchers hope to cut off the tumor supply of oxygen and nutrients, which in turn might stop the tumor from growing and spreading to other parts of the body.
In the 1980s, the pharmaceutical industry applied these concepts in the treatment of disease by creating new therapeutic compounds for modulating new blood vessel in tumor growth. In 2004 Avastin (bevacizumab), a humanized anti-VEGF monoclonal antibody was the first angiogenesis inhibitor approved by the Food and Drug Administration for the treatment of colorectal cancer. It has been estimated that over 20,000 cancer patients worldwide have received experimental forms of anti-angiogenic therapy.
Angiogenesis represents an excellent therapeutic target for the treatment of cardiovascular disease. It is a potent, physiological process that underlies the natural manner in which our bodies respond to a diminution of blood supply to vital organs, namely the production of new collateral vessels to overcome the ischemic insult.
A decade of clinical testing, both gene and protein-based therapies designed to stimulate angiogenesis in under perfused tissues and organs has resulted in disappointing results; however, results from more recent studies with redesigned clinical protocols have given new hope that angiogenesis therapy will become a preferred treatment for sufferers of cardiovascular disease resulting from occluded or stenotic vessels.